Electrical load management systems for allowing an electrical utility to control the load on the electrical system are known in the art. These systems operate to divert energy requirements to minimize electrical blackouts or "brown-outs". For example, U.S. Pat. No. 4,190,800 to Kelly, Jr., et al., entitled "Electrical Load Management System", assigned to the same assignee as the present invention, discloses an electrical load management system wherein a central station monitors the use of electrical power, and when peak demand periods occur, transmits coded information by radio from a central station to remote receivers mounted proximate the electrical loads. In this patent, the transmitted signal includes address and command information which is decoded at the receivers. Receivers which have been addressed pass command information over the distribution lines to the electrical loads, and thereby controls the operation of the customers' power consuming devices.
Other load management systems employ separate radio receivers at each customer's location, rather than providing a receiver at the distribution transformer as in the aforementioned U.S. patent. Examples of this type system include the types DCU-1120, -1170, -1180, and -1190 utility radio switches manufactured by Scientific-Atlanta, Inc., Atlanta, Ga., and the type REMS-100 radio switch manufactured by General Electric, King of Prussia, Pa. These systems incorporate an FM receiver which can receive a transmittal up to about 25 miles from a transmitter site. The transmitter issues commands to temporarily remove power from a selected load. This self-contained receiver is typically mounted on or immediately adjacent to the electrical loads under control, and receives its power from the line that feeds the controlled loads. Switches, jumpers, or other means contained within the receiver configure the receiver to respond only to a particular address or set of addresses, so that different geographical areas, types of appliances, or numbers of consumers may be separately controlled.
A particular problem with these separate remotely-controllable radio switches for electrical load management is testing of individual receivers for responsiveness. In particular, for effective load management the utility must develop a high degree of certainty that selected electrical loads will be removed when the commands are transmitted. If certain receivers are malfunctioning or are located in fringe reception areas wherein command signals may not reliably reach the receivers, there will be uncertainty whether a given command to reduce a load in an emergency situation will remove enough of the load to prevent a brown-out or other potentially more serious power interruption.
In the above-described General Electric REMS-100 radio switch, an optional light-emitting diode (LED) is provided for test purposes. The receiver is responsive to receipt of a particular transmitted test command to illuminate the LED, and as meters are manually read by the utility, the LED can be checked. This test function allows a check of correct wiring of the receiver, correct operation of the receiver, and a check on the radio signal, and remains on indefinitely until commanded off or until loss of power, and provides no other indicating function.
A handheld transmitter may be used for testing these receivers, but verifying the correct and reliable operation of the receiver requires a check of the system signal propagation properties. Thus sending test signals from the central utility transmitter, with the response indicated at each receiver site, is preferable for testing. However, the REMS-100 receiver only has one indicator light for a one-time test which is verified later by the utility. There is also no provision for testing any function other than correct wiring and simple yes-or-no one-time receipt of the particular test command by the receiver.
The particular REMS-100 load reduction receiver described above does however include a built-in volatile memory for maintaining an on-going record of valid messages received. This record is reset to zero by a particular predetermined incoming radio message, or upon power loss and restoration. Statistical data related to the number of load shedding commands provided to a particular receiver may be counted and retained in the volatile memory. This information is valuable in evaluating system performance, fringe area performance, and expansion coverage. However, the counting of the stored messages in the volatile memory entails opening of the receiver enclosure and placing an external probe on certain pins of the internal memory counter. Opening of the unit requires removal of the utility security tags or seals, and results in inconvenience to meter readers who must first remove the security tag, open the enclosure, connect a reading device to the memory, remove the connector after reading the memory contents, close the enclosure, and replace the security tag. In addition to risking the integrity of the circuitry by manual placement of a probe onto the pins of the circuits, this procedure involves the expenditure of a great amount of time, effort, and money in opening the box, reading the memory counter, and replacing the security tag or seal.
Accordingly, there is a need for a method of testing load management system receivers quickly and inexpensively and without inconvenient procedures such as breaking security tags or seals, risking the physical integrity of the circuitry, or adding costly or complex circuit components into the receiver.
While data displays are known in the art, and could easily be provided at each receiver for displaying more comprehensive testing information, complex data displays such as digital LED or liquid-crystal information displays are expensive and would require modifying the receiver enclosure so that the data display could be viewed from the exterior of the receiver enclosure.